Stabilized direct current supply circuit



Oct. 3, 1967 P. s. SCHERMANN 3,345,553

STABILIZED DIRECT CURRENT SUPPLY CIRCUIT Filed April 27, 1964 P5752 \SZ/LA/QDSKA/EPMA/V/V INVENTOR.

United States Patent ABSTRACT OF THE DISCLOSURE A transistor has its emitter-collector path connected to a load, and its base-emitter path connected in parallel to a stabilizing voltage, obtained from a voltage divider; the emitter is connected by means of a resistor 8 to the output and an additional resistor 9, forming a voltage divider with resist-or 8, is connected to the input to apply input variations inversely to the emitter and further stabilized output current.

The invention relates to a transistor circuit for supplying a stabilized direct current to a load circuit, and more particularly to a regulated transistor current supply circuit immune to wide swings of input voltage.

A circuit of that type has already been proposed in which the collector electrode of a regulating transistor is connected to a source of a direct voltage through the load terminals and its emitter electrode is connected to the source of direct voltage through an emitter resistor, the base electrode and the end of the resistor which is not connected to the emitter being connected to the tap, and one end respectively, of a voltage-stabilized voltage divider which is connected to an input voltage source and which is so adapted that variations of the input direct voltage give rise to relatively much smaller variations of the voltage between the base electrode and the end of the emitter resistor which is not connected to the emitter electrode. s

In this circuit arrangement, the voltage stabilized voltage divider provides a voltage which is not strongly dependent upon the input voltage and which is compared with a feedback-voltage, consisting of the sum of the voltage drop across the emitter resist-or and the baseemitter voltage of the transistor.

Since the emitter current of the transistor bears a fixed relation to its collector current and since these two currents are determined almost exclusively by the base-emitter voltage, this makes automatically for a value of the collector current, at which the sum of the voltage drop across the emitter resistor and the base-emitter voltage of the regulating transistor equals the reference voltage which is provided by the voltage-dependent voltage divider.

The above discussed relationships are valid within wide limits, independent of the collector direct voltage. Only if this direct voltage falls below the knee voltage or rises above the breakdown voltage, these limits have been reached, in which case the collector current falls below, or respectively, rises above the stabilized value.

The reference voltage can be generated in various ways. The most usual method is to assemble the voltage-dependent voltage divider from an ordinary resistor and a voltage stabilizer, such as a Zener diode, one or more selenium rectifiers in forward direction, an electrolytic voltage stabilizing cell or a glow discharge tube. It is also possible to generate a reference voltage by means of a current stabilizing device, such as an iron-hydrogen ballast lamp and a voltage stabilizing device.

3,345,553 Patented Oct. 3, 1967 ICC It has been found, however, that regardless of the way in which the voltage-dependent voltage divider is designed, the reference voltage is never entirely free from the influence of input voltage variations. If the input voltage rises above the nominal value, the reference voltage also rises somewhat, although to a much smaller extent, so that the output current increases somewhat. I

It is an object of the invention to provide a circuit in which the influence of input voltage variations is virtually entirely eliminated, so that the stability of the output is improved.

For that purpose, the regulator circuit according to the invention which is essentially similar to the circiut just discussed, is further provided with a resistor connected between the terminal of the input voltage source which is not connected to the emitter resistor and the emitter of the regulating transsitor. This additional resistor is of such value, that the influence of input voltage variations on the output current is compensated- The invention will be described below with reference to the accompanying drawing, which shows an embodiment of a device according to the invention.

Referring now to the figure, a voltage E is applied to the terminals 1 and 2, between which a voltage divider is connected, consisting of a resistor 3 and a Zener diode 4. The collector electrode of a regulating transistor 5 is connected to the terminal 2 through the load terminals 6 and 7 and a DC. voltage source 10, whilst the emitter electrode of the regulating transistor 5 is connected to the terminal 2 through an emitter resistor 8. The circuit as described so far is entirely conventional.

Across the Zener diode 4 a reference voltage is generated which is nearly independent of the input voltage.

According to the invention and in order to compensate for variations of the voltage across Zener diode 4, which can be caused by variations of the input voltage E,, a further resistor 9 is connected between the input terminal 1 and the emitter electrode of the regulating transistor 5.

In operation, this resistor 9 applies a voltage variation to the emitter electrode of the regulating transistor, which equals the variation of the reference voltage, so that the base-emitter voltage of the regulating transistor 5 remains constant and consequently the output current remains constant.

Assuming that the regulating transistor 5 does not load the voltage dividers 3, 4 and 9, 8 appreciably, which in practice usually applies, the value of the resistor 9 can be calculated as follows:

If the input voltage E, fluctuates with an amount AE, the voltage variation at the base electrode of the regulating transistor 5 amounts to Where R4 is the dynamic resistance of the Zener diode. Since an equal voltage variation must be applied to the emitter electrode of the regulating transistor 5, which is determined by R8 R9+R8' AE it follows:

As current stabilizing device any device can serve, the

resistance of which rises strongly with the current, such as an iron-hydrogen ballast lamp, whilst as voltage stabilizing device any device can serve, the resistance of which decreases strongly with increasing current,- such as a Zener diode, one or more selenium rectifiers in forward direction, an electrolytic voltage stabilizing cell, a glow discharge tube or a resistor with a negative voltage coefficient.

It is also possible, to replace the resistor 8 by a current stabilizing device in any of these possible circuit arrangements, in which case a still better stabilization of the output current can be obtained, since this is favoured by a high feedback ratio and consequently by a high dynamic resistance of the component 8.

The values of R3, R4, R8 and R9, refer to the dynamic resistances of the components under operative conditions,

rather than to the static resistance if they should be ditferent.

I claim: F

1. In a stabilized direct current circuit to supply direct current to a load,

a pair of input terminals (1, 2) adapted for connectionto a source of input voltage (E subject to variation;

a pair of output terminals (6, 7) providing a regulated current (I and a source of direct current (10) in series with said output terminals;

a voltage divider (3, 4) comprising at least one stabilizing circuit element (4) connected across said input terminals (1, 2);

and a transistor having an emitter resistance (8) connected to the emitter of the transistor (5), the collector-emitter path being in series with said load terminals, and the base-emitter path being in parallel with one of said elements (4) of the voltage divider;

the improvement comprising a further resistor (9) interconnecting the emitter and the other side of the other of said voltage divider elements (3), the further resistor (9) andsaidemitterresistance (8) :forminga second voltage divider connector across said input ter- I .minals (1, 2,).

2. Circuit as claimed .in claim 1 wherein the value of the further resistor (9) is:

wherein: R8 is the value of the emitter resistor (8); R3 is the value of the resistance of the voltage divider branch *between the one terminal (1) of the input voltage source and the base electrode of the regulating transistor (5);

and R4 is the value of resistance of the voltage divider branch between said electrode and the other terminal (2) of the input voltage source (E 3. Circuit as claimed in claim 2 wherein the resistance value of the stabilizing circuit element is its dynamic resistance.

'4. Circuit as claimed in claim 1 wherein the voltage divider (3, 4) consists of a resistor (3) connected between the terminal of the voltage source (1) which is not connected to the emitter resistor ('8) and the base electrode of the regulating transistor (5); and a stabilizing device (4) connected between the base electrode and the other terminal (2) of the voltage source.

5. Circuit as claimed in claim 4 wherein said stabilizing device is a Zener diode (4).

6. Circuit as claimed in claim 1 wherein said voltage divider consists of a current stabilizing device connected between the terminal of the voltage source (1) which is not connected to the emitter resistor (8) and the base electrode of the regulating transistor (5), and aresistor (4) connected between the base electrode of the regulating transistor (5) and the other terminal of the voltage source.

7. Circuit as claimed in claim 6 wherein said stabilizing circuit element is a iron-hydrogen ballast lamp.

8. Circuit as claimed in claim 1 wherein said voltage divider comprises a pair of stabilizing circuit elements; one of said elements being a current stabilizing device connected between the terminal of the input voltage source (1) which is not connected to the emitter resistor and the base electrode of the regulating transistor; the other stabilizing circuit element being a voltage stabilizing device connected between the base electrode of the regulating transistor and the other terminal (2) of the input voltage source.

9. Circuit as claimed in claim 8 wherein said current stabilizing device is a iron-hydrogen ballast lamp and said voltage stabilizing device is a Zener diode.

10. Circuit as claimed in claim '1 wherein the emitter resistor (8) includes a current stabilizing resistance element.

11. Circuit as claimed in claim 8 wherein said current stabilizing device is a iron-hydrogen ballast lamp and said voltage stabilizing device is a glow discharge tube.

References Cited UNITED STATES PATENTS 3,048,718 8/1962 Starzec -et al 323-22 3,214,668 10/1965 Brinster 323.22 3,227,942 1/1966 Brench et al 323-22 3,241,045 3/1966 Brousseau et a1. 323-22 JOHN .F. COUCH, Primary Examiner.

' L. WACHTELL, Assistant Examiner. 

1. IN A STABILIZED DIRECT CURRENT CIRCUIT TO SUPPLY DIRECT CURRENT TO A LOAD, A PAIR OF INPUT TERMINALS (1, 2) ADAPTED FOR CONNECTION TO A SOURCE OF INPUT VOLTAGE (E1) SUBJECT TO VARIATION; A PAIR OF OUTPUT TERMINALS (6, 7) PROVIDING A REGULATED CURRENT (IO); AND A SOURCE OF DIRECT CURRENT (10) IN SERIES WITH SAID OUTPUT TERMINALS; A VOLTAGE DIVIDER (3, 4) COMPRISING AT LEAST ONE STABILIZING CIRCUIT ELEMENT (4) CONNECTED ACROSS SAID INPUT TERMINALS (1, 2); AND A TRANSISTOR (5) HAVING AN EMITTER RESISTANCE (8) CONNECTED TO THE EMITTER OF THE TRANSISTOR (5), THE COLLECTOR-EMITTER PATH BEING IN SERIES WITH SAID LOAD TERMINALS, AND THE BASE-EMITTER PATH BEING IN PARALLEL WITH ONE OF SAID ELEMENTS (4) OF THE VOLTAGE DIVIDER; THE IMPROVEMENT COMPRISING A FURTHER RESISTOR (9) INTERCONNECTING THE EMITTER AND THE OTHER SIDE OF THE OTHER OF SAID VOLTAGE DIVIDER ELEMENTS (3), THE FURTHER RESISTOR (9) AND SAID EMITTER RESISTANCE (8) FORMING A SECOND VOLTAGE DIVIDER CONNECTOR ACROSS SAID INPUT TERMINALS (1, 2). 